2002 Annual

Wednesday, 16 January 2002: 4:29 PM
Cloud liquid water path variation with temperature during SHEBA/FIRE-ACE
Alice Fan, SAIC, Hampton, VA; and B. Lin, P. Minnis, and D. Spangenberg
Poster PDF (43.8 kB)
Polar regions are of great interest for climate change studies because of their high sensitivity to global warming. The SHEBA (Surface Heat Budget of the Arctic Ocean/First International Satellite Cloud Climatology Project(ISCCP) Regional Experiment (FIRE) - Arctic Clouds Experiment (ACE) was undertaken to gain insight on Arctic clouds.

This study evaluates the amount of liquid water path (LWP) variation with cloud temperature during the FIRE - ACE (May ~ Aug. 1998). The cloud amounts are derived from AVHRR data of NOAA-12 and 14 satellites around SHEBA site. The LWP values are retrieved from ground-based microwave measurements using an algorithm adopted from satellite remote sensing. This method accounts for the temperature dependence of cloud water absorption and atmosphere gas absorption.

Only the overcast measurements with LWP amount between 0.02 mm and 1.0 mm are selected for analysis to exclude the unrealistically detected clouds caused by instrumental noise and retrieval errors, and the possible rain. After collocating these measurements with satellite data, only 137 overcast cases are available. Based on these cases, with cloud temperature varying from 230 to 282, the analysis results indicate that LWP amount and cloud physical thickness increases with cloud warming. The cause of thickening is the descent of cloud-base and ascent of cloud-top. These phenomena are different from those observed at mid-latitude regions.

The correlation coefficients between LWP amount and cloud temperature and cloud thickness are 0.3 and 0.47, respectively, which is statistically significant at 99% confidence level. They indicate LWP amount increases when cloud temperature increases and when clouds thicken. Also, cloud thickness (or LWP amount) are strongly correlated to cloud-top and cloud-base heights. For all LWP data (~8000 samples) estimated during FIRE-ACE, consistent LWP dependences on temperature and cloud base height were found.

Supplementary URL: http://